Fungi from Mauritius: Anthostomella species on Pandanus

Mycol. Res. 102 (11) : 1319–1324 (1998)

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Fungi from Mauritius : Anthostomella species on Pandanus

R. D U L Y M A M O DE1, P. F. C A N N O N2 A N D A. P E E R A L L Y3 " Faculty of Science, University of Mauritius, ReU duit, Mauritius # CABI Bioscience, Bakeham Lane, Egham, Surrey TW20 9TY, U.K. $ University of Mauritius, ReU duit, Mauritius

Anthostomella petrinensis and A. theobromina are described from endemic Pandanus species in Mauritius. They are compared with other Anthostomella species reported on Pandanaceae and Palmae. A table is included, facilitating comparison between the new species and previously published taxa with similarly sized ascospores.

Studies of fungi collected on endemic Pandanus species in the remaining native forest of Mauritius have revealed two interesting Anthostomella species distinct from other described taxa. Pandanus, the principal genus of the Pandanaceae, is a characteristic component of tropical vegetation. Recent studies of microfungi associated with this genus have revealed very considerable diversity (McKenzie & Hyde, 1997), but this paper reports on the first studies of fungi from this host group within the Mascarene region. The host plants have some parallels in their physical structure with the Palmae, and a number of fungus groups show evolutionary radiation within these two families (e.g. Hyde, 1994 b, 1997). We have, therefore, compared our species of Anthostomella particularly with taxa recorded from species of Palmae and Pandanaceae. There are more than 300 species described in Anthostomella, and many of these (especially tropical representatives) are inadequately studied. Major taxonomic contributions to this genus have been by Francis (1975), Hyde (1994 a, 1996), and Rappaz (1995). In a recent review of Anthostomella on palms and Pandanus, Hyde (1996) accepted 28 species, five occurring on Pandanus. These are A. baileyi S. M. Francis, A. lucens Sacc., A. minutoides K. D. Hyde, A. pandani (Rabenh.) Sacc. and A. phoenicicola Speg. None of these species has been encountered to date in Mauritius. MATERIALS AND METHODS Field collections were made from Pandanus rigidifolius Vaughan & Wiehe and P. palustris Thouars from Pe! trin Reserve and P. eydouxia Balf. f. from the Perrier Reserve, Mauritius. Labelled materials were air-dried and microscopical studies were carried out partly in the Mycology Laboratory at the University of Mauritius and partly at IMI. Materials for microscopical studies were mounted in water, lactofuchsin, Melzer’s reagent or cotton-blue in lactic acid. Camera lucida drawings were

made using an Olympus BH2 microscope and fungi were photographed with a Zeiss photomicroscope. All material was illustrated, and measurements made, from slides mounted in lactofuchsin. Material is deposited in the Mycological Herbarium of the University of Mauritius, with some duplicate specimens at IMI. Anthostomella petrinensis Dulymamode, P. F. Cannon & Peerally, sp. nov. (Figs 1–3, 7, 10). Etym. : petrinensis, derived from Pe! trin, the locality from which the fungus was collected. Ascomata 160–250¬180–260 µm, globosa vel subglobosa, immersa, nullo collo. Clypeus nebulosus, 30–50 µm crassus. Paraphyses 2–4 µm diam., evanescentes, septatae. Periphyses 12–14¬2–3 µm, copiosae. Asci 82–104¬10–14 µm, cylindrici, brevistipitati, crassitunicati ubi juvenes vel paulo tenuitunicati ad maturitatem, apice rotundato vel leviter truncato, annulo apicali amyloideo, ca 4±5 µm diam., ca 2 µm crasso, octospori. Ascosporae uniseriales, 12–14¬7–9 µm, ovoideae vel ellipsoideae, atrobrunnescentes, crassitunicatae, rima germinationis recta, ! 1 µm crassa, vagina et appendices desunt. Anamorph non visus.

Ascomata visible from the surface as scattered small greyish white spots ca 50 µm diam., which are clusters of partially extruded periphyses ; 160–250¬180–260 µm ; globose to subglobose, completely immersed, hardly raising the substrate surface, neck absent. Clypeus ill-defined, reduced to a narrow circular rim 30–50 µm thick around the ostiole. Peridium 10–15 µm thick, composed of an outer layer of host cells filled with angular fungal tissue and completely occluded by melanin deposits, and an inner layer of sometimes compressed dark brown thick-walled fungal cells. Paraphyses hypha-like, 2–4 µm wide, deliquescing at maturity, septate, rarely branching. Periphyses 12–14¬2–3 µm, copious, with rounded tips. Asci 92–104¬10–14 µm, cylindrical, short-stalked, thickwalled when young but rather thin-walled at maturity, the

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1 3

2

Figs 1–3. Anthostomella petrinensis (holotype). Fig. 1. Vertical section through ascoma (bar, 100 µm). Fig. 2. Ascospores (bar, 10 µm). Fig. 3. Asci and paraphyses (bar, 20 µm).

4

6

5

Figs 4–6. Anthostomella theobromina (holotype). Fig. 4. Vertical section through ascoma (bar, 100 µm). Fig. 5. Ascospores (bar, 10 µm). Fig. 6. Asci and paraphyses (bar, 20 µm).

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Figs 7–9. Light micrographs of asci and ascospores. Fig. 7. Anthostomella petrinensis (holotype). Figs 8–9. A. theobromina (holotype) ; bar, 20 µm.

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Figs 10–11. Vertical sections of ascomata. Fig. 10. Anthostomella petrinensis (holotype). Fig. 11. A. theobromina (holotype) ; bar, 50 µm.

apex rounded to slightly truncate with a discoid iodinepositive ring ca 4±5 µm diam. and ca 2 µm deep, eight-spored. Ascospores arranged uniseriately and obliquely, 12–14¬ 7–9 µm, ovoid-ellipsoidal, becoming very dark brown, thickwalled with a straight slightly raised germ slit ! 1 µm wide extending over the whole length of the spore. Sheath and appendages not seen. Anamorph unknown. Typification : Mauritius : Pe! trin Reserve, outside fence near rivulet, on the abaxial surface of a dead, fallen leaf of Pandanus rigidifolius, 11 Nov. 1996, R. Dulymamode P128 (mycol. herb. Univ. Mauritius – holotype ; IMI 375400 – isotype). Host species : Pandanus rigidifolius. Distribution : Mauritius ; only known from a single locality. This species shares ascospore features with A. livistonicola (Hyde, 1994a), but differs with respect to its longer asci, peridial structure, ascomatal size, and the apparent absence of a mucous sheath. Whilst the difference in ascomatal size could be attributed to the host, the other differences noted are likely to be properties of the fungus rather than the host}fungus interaction. We are, therefore, confident that A. petrinensis is a separate species. We have not cultured this species, but a Nodulisporium-like fungus occurs sparsely on the surface of the dead leaf material, which might be its anamorph. Of other species of Anthostomella which have been studied recently, A. anserina (Pers.) Rappaz has similarly sized ascospores (Rappaz, 1995). The clypeus in this species is, however, large and prominent, and the asci are long-stalked compared with those of A. petrinensis. In addition, the ascospores of A. anserina are slightly narrower but more strongly navicular, and have a small hyaline cell at one end. A.

anserina is a European species, apparently saprobic on a wide range of plants. A. spartii Berl. & Voglino has similar ascospores (Francis, 1975), but they have a narrow gelatinous sheath which is lacking in A. petrinensis, and the ascomata are larger and thicker-walled in the former species. A. spartii is currently known only from the Mediterranean region. Table 1 summarizes the differences between these taxa. Pandanus rigidifolius is endemic to Mauritius, occurring only in the Black River Gorges National Park in the south-west of the island, although it is not immediately threatened with extinction. Despite intensive studies of other Pandanus species, we have only found A. petrinensis associated with this one species, in a single locality. Its conservation should, therefore, be considered. Other specimen examined : same locality and host, 14 Oct. 1996, R. Dulymamode P126 (mycol. herb. Univ. Mauritius).

Anthostomella theobromina Dulymamode, P. F. Cannon & Peerally, sp. nov. (Figs 4–6, 8–9, 11) Etym. : theobrominus, chocolate brown ; referring to the colour of the mature ascospores. Ascomata 230–340¬180–280 µm, globosa vel subglobosa, nigra, nullo collo, ostiolo 60–90 µm diam. Clypeus bene evolutus, 140–180 µm diam., 40–50 µm crassus. Peridium 15–25 µm crassum. Paraphyses 3–7 µm diam., septatae, apicibus obtusis, evanescentes. Periphyses copiosae, cylindricae. Asci 100–145¬15–21 µm, cylindrici, brevistipitati, crassitunicati ubi juvenes vel paulo tenuitunicati ad maturitatem, apice rotundato, annulo apicali 4–5 µm diam. et 1±5–2 µm crasso, in iodo non caerulescenti, octospori. Ascospores uniseriatae, 16–20¬9–13 µm, plus minusve ellipsoideae, saepe inaequilaterales, apicibus plus minusve acutis, atrobrunnescentes, rima germinationis recta, ! 1 µm crassa et vagina mucosa 2–3 µm crassa. Anamorph non visus.

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Table 1. Summary of morphological features of Anthostomella petrinensis, A. theobromina and similar species

Host Origin Ascomata

Clypei Peridia

Ostioles Asci

Apical rings Ascospores

Germ slits Secondary cells Sheaths

A. petrinensis

A. theobromina

A. anserina (Rappaz, 1995)

A. diderma (Rappaz, 1995)

A. lucens (Hyde, 1996)

A. spartii Francis (1975)

Pandanus Mauritius 160–250 ¬180–260 µm, globose to subglobose 30–50 µm wide, ill-defined 10–15 µm thick, of compressed cells

Pandanus Mauritius 230–340 ¬180–280 µm, globose to subglobose 140–180¬40–50 µm

Plurivorous Europe 500–1000 ¬400–600 µm, semiglobose, conical above 500–1000 µm wide

Unknown wood Eastern U.S.A. 500–800 ¬400–600 µm, globose

Pandanus, palms S.E. Asia ca 180¬60 µm, lenticular

Plurivorous Mediterranean 200–300 ¬240–260 µm, ³globose

15–25 µm thick, of 25–30 µm thick, thick-walled angular prosenchymatous cells

20–30 µm diam., 60–90 µm diam., 120–150 µm diam. periphysate periphysate 82–104¬10–14 µm, 100–145¬15–21 µm 110–180¬8–10 µm, short-stalked short-stalked stalk 30–80 µm long 4¬3–4 µm, tapered, 4±5¬2 µm, discoid, 4–5¬1±5–2 µm, discoid, I− I+ I+ 12–14¬7–9 µm, 16–20¬9–13 µm, 11–18±5¬6–8 µm, ovoid-ellipsoidal ellipsoidal to ellipsoidal, ends navicular rounded to truncate Straight Straight Straight Absent Absent Present Absent Present, 2–3 µm thick Slimy cap at one end

Ascomata visible from the surface as a circular greyish area 150–260 µm diam. with a central black ostiole surrounded by a greyish white rim ; in older specimens epidermal tissues detach to expose the black clypeus ; 230–340¬180–280 µm, globose to subglobose, black, the neck absent, ostiole 60–90 µm diam. Clypeus black, slightly raised around the ostiole, 140–180 µm diam., 40–50 µm thick. Peridium 15–25 µm thick, thicker at the base, with a thick outer layer of ³angular cells which are completely occluded by melanin deposits, and a thin inner layer of paler compressed cells. Paraphyses hypha-like, as long as the asci, 3–7 µm diam., septate with rounded apices, deliquescing in older specimens. Periphyses numerous, cylindrical with ³rounded tips. Asci 100–145¬15–21 µm, cylindrical, the stalk very much reduced, thick-walled when young but becoming thinner at maturity, the apex rounded with an apical ring 4–5 µm wide and 1±5–2 µm deep, not blueing in iodine, eight-spored. Ascospores arranged uniseriately, 16–20¬9–13 µm, ³ ellipsoidal, often inaequilateral (navicular), the ends ³ acute, becoming dark brown, with a straight germ slit ca 1 µm wide extending over the whole length of the spore on the rounded side and a mucous sheath 2–3 µm thick. Anamorph not seen. Typification : Mauritius : Perrier Reserve, on abaxial and adaxial surfaces of dead fallen leaves of Pandanus eydouxia, 27 July 1996, R. Dulymamode P89 (mycol. herb. Univ. Mauritius – holotype ; IMI 375401 – isotype). Host species : Pandanus palustris, P. eydouxia. Distribution : Mauritius ; only known from two localities.

1000–1500¬120 µm 320–450 µm wide

Ill-defined

Prosenchymatous

Of host cells filled with hyphae

ca 100 µm diam.

—

18–23 µm thick, thick-walled outside with a hyaline compressed inner layer —

130–150¬8–10 µm, 110–140¬9–12 µm, 98–121¬10–11 µm, stalk 20–30 µm long-stalked with a short tapered stalk 4±5–5¬2±5–3 µm, 4–5¬3–4 µm, 5¬1±5 µm, slightly tapered, I+ stopper-shaped, I+ tapered, I+ 17–19¬9–11 µm, 15–18¬7–9 µm, 12–15¬8–9 µm, ellipsoidal ellipsoidal, broadly ellipsoidal inaequilateral Straight or sinuous Straight Straight Present Absent Absent Absent Present, thin Present, narrow

Amongst the described Anthostomella species with ascospores ca 20 µm long, A. dilatata (Berk. & Broome) Petch matches this fungus in ascospore size but has rounded ends rather than the distinctly pointed ones evident in A. theobromina (Hyde, 1996). In addition, the asci of A. dilatata are much shorter (reaching only 70 µm), and completely lack apical rings. In common with most species of the Xylariaceae, Anthostomella species typically have asci with iodine-positive apical rings, but a number of other species are known where the ring either does not blue in iodine, or is lacking altogether (Francis, 1975 ; Hyde, 1996). In our experience, iodine reactions in ascus rings are frequently unreliable unless the material is completely fresh. Some other species of Anthostomella have similarly sized ascospores to those of A. theobromina. A. diderma (Schwein.) Rappaz (Rappaz, 1995) has much larger ascomata and clypei, asci with an iodine-positive apical ring, and ascospores with a small hyaline cell at one end, in contrast to the sheathed spores of A. theobromina. A. diderma is known from a single collection on unknown decorticated wood from the eastern U.S.A. A. lucens Sacc. is known from palms and Pandanus in S.E. Asia. This species again has similar ascospores to those of A. theobromina, but the ascomata are lenticular with a pronounced clypeus, rather than globose with a reduced clypeus. A. lucens has asci with an iodine-positive ring which is much thicker than the iodine-negative structures seen in A. theobromina. Table 1 summarizes the differences between these taxa. Anthostomella theobromina is known from two host species, both endemic to Mauritius. Pandanus palustris is critically endangered, being reduced to less than five plants in a restricted

Fungi from Mauritius area outside the boundaries of the Pe! trin reserve. P. eydouxia occurs in various localities of upland Mauritius especially along river margins, in relatively small populations. A further collection on P. rigidifolius from the same locality (Dulymamode P23) has a much smaller clypeus and slightly smaller ascospores. It might represent a further new species, but asci were not found and we prefer not to introduce a new taxon at present. Other specimens examined : Mauritius : Pe! trin, outside reserve, on adaxial surface of dead, fallen leaf of P. palustris, 31 Aug. 1996, R. Dulymamode P35 (mycol. herb. Univ. Mauritius ; IMI 375402) ; Perrier Reserve, on abaxial and adaxial surfaces of dead fallen leaves of P. eydouxia, 26 Aug. 1996, R. Dulymamode P89a (mycol. herb. Univ. Mauritius). (Accepted 28 January 1998)

1324 REFERENCES Francis, S. M. (1975). Anthostomella Sacc. (Part I). Mycological Papers 139, 1–97. Hyde, K. D. (1994 a). Fungi from rachides of Livistona in Papua New Guinea. Botanical Journal of the Linnean Society 115, 315–324. Hyde, K. D. (1994 b). Fungi from palms. XIII. The genus Oxydothis, a revision. Sydowia 46, 265–314. Hyde, K. D. (1996). Fungi from palms. XXVI. The genus Anthostomella with ten new species. Nova Hedwigia 62, 273–340. Hyde, K. D. (1997). Additions to the genus Linocarpon (Ascomycetes : Hyponectriaceae). Botanical Journal of the Linnean Society 123, 109–131. McKenzie, E. H. C. & Hyde, K. D. (1997). Microfungi on Pandanaceae. In Biodiversity of Tropical Microfungi (ed. K. D. Hyde), pp. 157–177. Hong Kong University Press : Hong Kong. Rappaz, F. (1995). Anthostomella and related xylariaceous fungi on hard wood from Europe and North America. Mycologia Helvetica 7, 99–168.